The SNP MEP will challenge Angus Robertson for the vacancy which has arisen following Stewart Hosie’s decision to step down after reports he was having an affair with a journalist.
Mr Hosie’s resignation as Nicola Sturgeon’s number two followed the revelations that he had an extra-marital relationship with Serena Cowdy.
He has since left his wife Shona Robison, the SNP Health Secretary and a close friend of Ms Sturgeon.
Mr Robertson, the SNP Westminster leader, has been considered the favourite to succeed Mr Hosie.
The Scotsman has learned that Mr Smith intends to announce his intention to enter the race this week, which has also seen Christopher McEleny, leader of the SNP group on Inverclyde Council throw his hat into the ring.
Mr Smith has been an MEP since 2003 and his recent speech in the European Parliament following the Brexit vote saw him gain international prominence. He implored EU politicians not to “let Scotland down” after a majority for staying in the bloc was recorded north of the Border.
Ahead of his announcement, Mr Smith claimed there were flaws in the SNP’s EU arguments during the 2014 independence referendum.
He underlined his commitment to a second Scottish independence referendum as the best way of keeping Scotland’s place in the EU.
“If we are serious about retaining all the benefits of the EU, then independence is the clearest way to do it and we did all the groundwork in 2014,” he said.
However, he also acknowledged that mistakes had been made in the past when it came to SNP pro-independence arguments and the EU. During the 2014 referendum the SNP leadership claimed an independent Scotland would automatically remain in the EU despite warnings that Scotland would have to go to the back of the queue to obtain membership.
Mr Smith said: “The biggest lesson, other than the position of currency, is that we didn’t prepare the EU membership case properly. We boxed ourselves into a position where we used word like ‘automatic’ over a process that is anything but automatic.
“We spoke to London embassies rather than capitals, and to London journalists rather than the European ones back at home. We need to remedy that. We cannot allow our position to be articulated through the London prism. I can play that role with credibility, but being Depute will make that a much stronger proposition. It will demonstrate to the party, Scotland and the wider world that we are serious about this.”
Mr Smith believes his background as an MEP and committed Europhile makes him a good candidate to be Depute Leader.
He said: There is a role and a need to have an advocate for Scotland internationally, whatever happens. We need to keep the EU member state capitals abreast of what Scotland thinks. We must go to these places and brief the ministers. They will be sitting round the table – Scotland won’t and the UK won’t. I can do that in a way that I don’t see anyone else can.”
Born in Glasgow, Mr Smith grew up in Saudi Arabia. Before becoming an MEP he was a corporate lawyer.